linux-kernel - Re: [PATCH v4 1/2] serial: sifive: lock port in startup()/shutdown() callbacks

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Message-Id: <20250405112307.485386-1-ryotkkr98@gmail.com>
Date: Sat,  5 Apr 2025 20:23:07 +0900
From: Ryo Takakura <ryotkkr98@...il.com>
To: gregkh@...uxfoundation.org
Cc: alex@...ti.fr,
	aou@...s.berkeley.edu,
	bigeasy@...utronix.de,
	conor.dooley@...rochip.com,
	jirislaby@...nel.org,
	john.ogness@...utronix.de,
	linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	linux-serial@...r.kernel.org,
	palmer@...belt.com,
	paul.walmsley@...ive.com,
	pmladek@...e.com,
	ryotkkr98@...il.com,
	samuel.holland@...ive.com,
	stable@...r.kernel.org,
	u.kleine-koenig@...libre.com
Subject: Re: [PATCH v4 1/2] serial: sifive: lock port in startup()/shutdown() callbacks

Hi Greg, thanks for the comments!

On Sat, 5 Apr 2025 08:35:44 +0100, Greg KH wrote:
>On Sat, Apr 05, 2025 at 01:43:38PM +0900, Ryo Takakura wrote:
>> startup()/shutdown() callbacks access SIFIVE_SERIAL_IE_OFFS.
>> The register is also accessed from write() callback.
>> 
>> If console were printing and startup()/shutdown() callback
>> gets called, its access to the register could be overwritten.
>> 
>> Add port->lock to startup()/shutdown() callbacks to make sure
>> their access to SIFIVE_SERIAL_IE_OFFS is synchronized against
>> write() callback.
>> 
>> Signed-off-by: Ryo Takakura <ryotkkr98@...il.com>
>> Cc: stable@...r.kernel.org
>
>What commit id does this fix?

I believe the issue existed ever since the driver was added by commit 
45c054d0815b ("tty: serial: add driver for the SiFive UART").

>Why does patch 1/2 need to go to stable, but patch 2/2 does not?  Please

The patch 2/2 has nothing to do with existing issue and its only the 
patch 1/2 that needs to go to stable as discussed [0].

>do not mix changes like this in the same series, otherwise we have to
>split them up manually when we apply them to the different branches,
>right?

I see, I'll keep this in mind.
Let me resend the two separately with 'Fixes:' tag for the patch 1/2. 

Sincerely,
Ryo Takakura

>thanks,
>
>greg k-h

[0] https://lore.kernel.org/lkml/84sen2fo4b.fsf@jogness.linutronix.de/